| 1,47 → 1,45 |
|---|
| # memset() Author: Kees J. Bot |
| # 2 Jan 1994 |
| # void *memset(void *s, int c, size_t n) |
| # Set a chunk of memory to the same byte value. |
| # |
| /* memset() Author: Kees J. Bot */ |
| /* 2 Jan 1994 */ |
| |
| .intel_syntax |
| /* void *memset(void *s, int c, size_t n) */ |
| /* Set a chunk of memory to the same byte value. */ |
| /* */ |
| #include "asm.h" |
| |
| .global _memset |
| |
| .text |
| .align 16 |
| _memset: |
| push ebp |
| mov ebp, esp |
| push edi |
| mov edi, [8+ebp] # The string |
| movzx eax, byte ptr [12+ebp] # The fill byte |
| mov ecx, [16+ebp] # Length |
| ENTRY(memset) |
| push %ebp |
| movl %esp, %ebp |
| push %edi |
| movl 8(%ebp), %edi /* The string */ |
| movzbl 12(%ebp), %eax /* The fill byte */ |
| movl 16(%ebp), %ecx /* Length */ |
| cld |
| cmp ecx, 16 |
| jb sbyte # Don't bother being smart with short arrays |
| test edi, 1 |
| jnz sbyte # Bit 0 set, use byte store |
| test edi, 2 |
| jnz sword # Bit 1 set, use word store |
| cmpl $16, %ecx |
| jb sbyte /* Don't bother being smart with short arrays */ |
| testl $1, %edi |
| jne sbyte /* Bit 0 set, use byte store */ |
| testl $2, %edi |
| jne sword /* Bit 1 set, use word store */ |
| slword: |
| movb ah, al |
| mov edx, eax |
| sal edx, 16 |
| or eax, edx # One byte to four bytes |
| shrd edx, ecx, 2 # Save low two bits of ecx in edx |
| shr ecx, 2 |
| rep stosd # Store longwords. |
| shld ecx, edx, 2 # Restore low two bits |
| movb %al, %ah |
| movl %eax, %edx |
| sall $16, %edx |
| orl %edx, %eax /* One byte to four bytes */ |
| shrdl $2, %ecx, %edx /* Save low two bits of ecx in edx */ |
| shrl $2, %ecx |
| |
| rep stosl /* Store longwords. */ |
| shldl $2, %edx, %ecx /* Restore low two bits */ |
| sword: |
| movb ah, al # One byte to two bytes |
| shr ecx, 1 |
| rep stosw # Store words |
| adc ecx, ecx # One more byte? |
| movb %al, %ah /* One byte to two bytes */ |
| shrl $1, %ecx |
| |
| rep stosw /* Store words */ |
| adcl %ecx, %ecx /* One more byte? */ |
| sbyte: |
| rep stosb # Store bytes |
| rep stosb /* Store bytes */ |
| done: |
| mov eax, [8+ebp] # Return some value you have no need for |
| pop edi |
| pop ebp |
| movl 8(%ebp), %eax /* Return some value you have no need for */ |
| pop %edi |
| pop %ebp |
| ret |